A Raney catalyst may be Raney iron, cobalt or silver and, particularly, can be Raney nickel.
Raney first prepared the Raney catalysts in the twenties in such a way that a metal, acting also alone as a catalyst, primarily nickel and cobalt, was alloyed with aluminum or an other, alkali-soluble metal and, after crushing the alloy, the alkali-soluble metal was dissolved preferably with potassium hydroxide from the alloy. In this way, a highly active metal sponge was obtained which, however, had pyrophoric properties [Rompp's Encyclopedia of Chemistry (in Hungarian) Vol. 4, pages 46 to 47, Ed. Muszaki Konyvkiado, Budapest (1984)].
It is known that pyrophoric metals pose a serious danger in reactions carried out in the presence of organic solvents since these metals are inflammable in the air and can cause fire or an explosion in more serious cases. For this reason, the active metal sponge is kept under water in the commercially available form.